Back in December 1976, NOAA released these plastic cards from Nantucket Shoals to get an idea of the movement of the Argo Merchant spilled oil. Several of these drift cards have been found over the years in Ireland and France.

March 6, 2014 -- More than 37 years after the Argo Merchant grounding and oil spill, a plastic "drift card" was found by retired postman and beachcomber, Chris Easton, on a heap of marine debris on a beach near Perranporth, Cornwall, England.

When the Argo Merchant ran aground, it was carrying 7.7 million gallons of No. 6 fuel oil, a heavy refined oil.

Its grounding was due to navigational errors. The vessel was found to be 24 miles off course, and carrying two unqualified crew as helmsman, a broken gyrocompass, outdated maps, and an inaccurate radio direction finder.